diff -r 341c18ae5cea usr/python/Lib/socket.py
--- a/usr/python/Lib/socket.py	Wed Aug 05 11:02:08 2015 -0600
+++ b/usr/python/Lib/socket.py	Thu Aug 06 08:06:14 2015 -0600
@@ -18,6 +18,7 @@
 gethostbyaddr() -- map an IP number or hostname to DNS info
 getservbyname() -- map a service name and a protocol name to a port number
 getprotobyname() -- map a protocol name (e.g. 'tcp') to a number
+getprotobynumber() -- map a protocol number (e.g. '6') to a name
 ntohs(), ntohl() -- convert 16, 32 bit int from network to host byte order
 htons(), htonl() -- convert 16, 32 bit int from host to network byte order
 inet_aton() -- convert IP addr string (123.45.67.89) to 32-bit packed format
diff -r 341c18ae5cea usr/python/Modules/socketmodule.c
--- a/usr/python/Modules/socketmodule.c	Wed Aug 05 11:02:08 2015 -0600
+++ b/usr/python/Modules/socketmodule.c	Thu Aug 06 08:06:14 2015 -0600
@@ -24,6 +24,7 @@
 - socket.gethostbyaddr(IP address) --> (hostname, [alias, ...], [IP addr, ...])
 - socket.gethostname() --> host name (string: 'spam' or 'spam.domain.com')
 - socket.getprotobyname(protocolname) --> protocol number
+- socket.getprotobynumber(protocolnumber) --> protocol name
 - socket.getservbyname(servicename[, protocolname]) --> port number
 - socket.getservbyport(portnumber[, protocolname]) --> service name
 - socket.socket([family[, type [, proto, fileno]]]) --> new socket object
@@ -4569,6 +4570,34 @@
 \n\
 Return the protocol number for the named protocol.  (Rarely used.)");
 
+/* Python interface to getprotobynumber(name).
+   This only returns the protocol name, since the other info is
+   already known or not useful (like the list of aliases). */
+
+/*ARGSUSED*/
+
+static PyObject *
+socket_getprotobynumber(PyObject *self, PyObject *args)
+{
+    int proto;
+    struct protoent *sp;
+    if (!PyArg_ParseTuple(args, "i:getprotobynumber", &proto))
+        return NULL;
+    Py_BEGIN_ALLOW_THREADS
+    sp = getprotobynumber(proto);
+    Py_END_ALLOW_THREADS
+    if (sp == NULL) {
+        PyErr_SetString(PyExc_OSError, "protocol not found");
+        return NULL;
+    }
+    return PyUnicode_FromString(sp->p_name);
+}
+
+PyDoc_STRVAR(getprotobynumber_doc,
+"getprotobynumber(unsigned int) -> str\n\
+\n\
+Return the protocol string for the protocol number.  (Rarely used.)");
+
 
 #ifndef NO_DUP
 /* dup() function for socket fds */
@@ -5431,6 +5460,8 @@
      METH_VARARGS, getservbyport_doc},
     {"getprotobyname",          socket_getprotobyname,
      METH_VARARGS, getprotobyname_doc},
+    {"getprotobynumber",          socket_getprotobynumber,
+     METH_VARARGS, getprotobynumber_doc},
 #ifndef NO_DUP
     {"dup",                     socket_dup,
      METH_O, dup_doc},